JP7715089B2 - X-ray image acquisition method - Google Patents

Description

This disclosure relates to a method for acquiring X-ray images.

There has been a known invention relating to an X-ray tomography apparatus that captures X-ray fluoroscopic images of a subject by rotating an X-ray source and a two-dimensional detector placed opposite the X-ray source on a circular orbital plane with the same center of rotation (see Patent Document 1 below). The X-ray tomography apparatus described in Patent Document 1 comprises an X-ray source, two-dimensional X-ray imaging means, rotation means, correction table, conversion means, and correction table creation means (paragraph 0031, claim 1, abstract, and Figure 1).

The X-ray source emits X-rays in a cone shape. The two-dimensional X-ray imaging means is positioned opposite the X-ray source and captures the X-rays that pass through the subject. The rotation means rotates the X-ray source and the two-dimensional X-ray imaging means on a circular orbit with the same center of rotation. The correction table stores correction constants for correcting distortion of the image caused by the two-dimensional X-ray imaging means. The conversion means converts the image captured by the two-dimensional X-ray imaging means into Cartesian coordinates predetermined for the two-dimensional detection means, based on the correction constants stored in the correction table.

The correction table creation means creates the correction table based on a predetermined procedure. This correction table creation means includes coordinate axis correction table creation means for creating conversion constants that make Cartesian coordinates parallel and perpendicular to the rotation axis. This conventional X-ray tomography device can correct images captured by the two-dimensional X-ray detection means to images that are parallel to the rotation axis and perpendicular to the mid-plane (Patent Document 1, paragraph 0125).

Japanese Patent Application Publication No. 9-173330

The above-mentioned conventional X-ray tomography apparatus is based on the assumption that the rotation means uses a high-precision circular scanning drive means commonly used in medical CT apparatuses (Patent Document 1, paragraphs 0052 and 0056, Figure 1). As a result, this conventional apparatus cannot use common motors such as those used in industrial robots, increasing the overall cost of the apparatus. Furthermore, this conventional apparatus makes it difficult to correct images when misalignment occurs between the subject and the X-ray source and two-dimensional X-ray imaging means in a direction parallel to the central axis of rotation.

This disclosure provides an X-ray image acquisition method that can acquire X-ray images with the deviation corrected even if the relative position and orientation between the X-ray imaging device and the subject deviates from a reference state when a two-dimensional X-ray image is captured by moving the X-ray imaging device and the subject relative to each other using a general motor.

One aspect of the present disclosure includes a process of arranging an X-ray imaging device and a calibration object having a rotationally symmetric three-dimensional shape and a plurality of portions with different radial dimensions perpendicular to the axis of symmetry, rotating the calibration object and the X-ray imaging device relative to each other around a rotation center axis that coincides with the axis of symmetry of the calibration object using a rotation device including a motor, and capturing a plurality of calibration images of the calibration object using the X-ray imaging device from a plurality of imaging positions where the two-dimensional shape of the calibration object is the same; and capturing a plurality of calibration images of the calibration object captured by the X-ray imaging device in a reference state in which the three-dimensional orthogonal coordinate systems of the X-ray imaging device and the calibration object are coincident. the feature amounts of the reference image and each of the calibration images are compared, and an image correction amount is calculated and recorded to make each of the calibration images coincide with the reference image; the subject and the X-ray imaging device are arranged opposite each other in the same manner as the calibration subject, and the rotation device is used to rotate the X-ray imaging device and the subject relatively around the rotation center axis, and the X-ray imaging device is used to capture multiple X-ray images of the subject from the multiple imaging positions; and the X-ray imaging device is used to acquire multiple corrected images by correcting each of the multiple X-ray images of the subject based on the image correction amount.

The X-ray image acquisition method according to the above aspect may include a step of constructing a 3D CT image of the subject using the plurality of corrected images.

In the X-ray image acquisition method according to the above aspect, the rotation device may include a rotation support table that rotates around the central axis of rotation while supporting the calibration subject or the subject, and an industrial robot that positions the X-ray imaging device facing the calibration subject or the subject.

In the X-ray image acquisition method according to the above aspect, the rotation device may include a mounting table for placing the calibration subject or the subject on the rotation axis, and an industrial robot that faces the calibration subject or the subject placed on the mounting table and rotates the X-ray imaging device around the rotation axis around the calibration subject or the subject.

In the X-ray image acquisition method according to the above aspect, the rotation device may include a first industrial robot that holds the calibration subject or the subject and positions it on the rotation axis, and a second industrial robot that holds the X-ray imaging device and positions it facing the calibration subject or the subject, and at least one of the first industrial robot and the second industrial robot may rotate the X-ray imaging device and the calibration subject or the subject relatively around the rotation axis.

According to the above aspects of the present disclosure, an X-ray image acquisition method can be provided that, when a two-dimensional X-ray image is captured by moving an X-ray imaging device and a subject relative to each other using a general motor, even if the relative position and orientation between the X-ray imaging device and the subject deviates from a reference state, can acquire an X-ray image in which the deviation has been corrected.

1 is a schematic diagram showing an apparatus configuration according to an embodiment of an X-ray image acquisition method of the present disclosure. FIG. 2 is a functional block diagram of a control device that constitutes the X-ray image acquisition apparatus shown in FIG. 1 . 1 is a flow diagram illustrating an embodiment of a method for acquiring an X-ray image according to the present disclosure. FIG. 2 is a perspective view showing a reference state of the X-ray imaging apparatus and the calibration subject shown in FIG. 1; 4B is a reference image taken by the X-ray imaging device of FIG. 4A. 2 is a perspective view showing deviations of the X-ray imaging apparatus and the calibration subject in FIG. 1 from a reference state; 5B is a calibration image taken by the X-ray imaging device of FIG. 5A. 2 is a perspective view showing deviations of the X-ray imaging apparatus and the calibration subject in FIG. 1 from a reference state; 6B is a calibration image taken by the X-ray imaging device of FIG. 6A. FIG. 2 is a schematic configuration diagram showing a modified example of the X-ray image acquisition device of FIG. 1 . FIG. 2 is a schematic configuration diagram showing a modified example of the X-ray image acquisition device of FIG. 1 .

An embodiment of the X-ray image acquisition method according to the present disclosure will be described below with reference to the drawings.

Figure 1 is a schematic diagram showing an example of an apparatus configuration according to one embodiment of the X-ray image acquisition method of the present disclosure. Figure 2 is a functional block diagram of the control device 4 that constitutes the X-ray image acquisition apparatus 1 shown in Figure 1. Figure 3 is a flow diagram showing one embodiment of the X-ray image acquisition method of the present disclosure.

The X-ray image acquisition method P of this embodiment shown in Figure 3 can be implemented, for example, by an X-ray image acquisition device 1 such as that shown in Figure 1. The X-ray image acquisition device 1 includes, for example, an X-ray imaging device 2, a rotation device 3, a control device 4, and a display device 5.

The X-ray imaging device 2 includes, for example, an X-ray generator 21 and an X-ray detector 22. The X-ray generator 21 is controlled, for example, by a control signal CS21 input from the control device 4, and irradiates a cone-shaped X-ray beam (cone beam) onto the subject O placed between the X-ray generator 21 and the X-ray detector 22. The X-ray detector 22 is controlled, for example, by a control signal CS22 input from the control device 4, and detects X-rays that have passed through the subject O and outputs an X-ray image RI of the subject O corresponding to the detected X-rays to the control device 4.

The X-ray detector 22 can be configured, for example, as a flat panel detector, a combination of an image intensifier and a visible light sensor such as a CMOS sensor, or an X-ray line sensor. The X-ray generator 21 and the X-ray detector 22 output, for example, their respective operating states AS21 and AS22 to the control device 4.

The rotation device 3 includes, for example, at least one of a rotation support table 31 and an industrial robot 32. In the example shown in Figure 1, the rotation device 3 is composed of one rotation support table 31 and two industrial robots 32. The rotation support table 31 and each industrial robot 32 are driven by a general industrial motor M, rather than a high-precision scanning drive device such as those used in medical CT devices.

The rotating support base 31 rotates the support base 311, which supports the subject O, around a central rotation axis A perpendicular to the support base 311, using a motor M built into the rotation drive unit 312. The rotation drive unit 312 rotates the support base 311 in response to a control signal CS31 input from the control device 4, and outputs the rotation angle θ31 of the support base 311 detected by an angle sensor to the control device 4.

The industrial robot 32 is, for example, a four- to seven-axis vertical articulated robot, with a motor M and an encoder built into each joint. In the example shown in FIG. 1, the X-ray detector 22 of the X-ray imaging device 2 is attached to an attachment at the tip of the first industrial robot 32A, and the X-ray generator 21 of the X-ray imaging device 2 is attached to an attachment at the tip of the second industrial robot 32B. Each industrial robot 32A, 32B receives control signals CS32A, CS32B from the control device 4 and outputs the rotation angles θ32A, θ32B of each joint to the control device 4.

The control device 4 is composed of, for example, a central processing unit (CPU), not shown, a memory, a timer, and one or more microcontrollers including input/output units. The control device 4 may also include a storage device such as a hard disk. As shown in FIG. 2, the control device 4 has, for example, an X-ray device control unit 41, a rotation device control unit 42, and an image processing unit 43. Each unit of the control device 4 shown in FIG. 2 represents a function of the control device 4 that is realized by, for example, the CPU executing a program stored in a memory or storage device.

The X-ray imaging device control unit 41 controls the operation of the X-ray imaging device 2. The X-ray imaging device control unit 41 includes, for example, an X-ray generator control unit 411 and an X-ray detector control unit 412. The X-ray generator control unit 411 outputs a control signal CS21 to the X-ray generator 21 based on, for example, the operating state AS21 input from the X-ray generator 21, to control the start, stop, and output of X-ray irradiation by the X-ray generator 21. The X-ray detector control unit 412 outputs a control signal CS22 to the X-ray detector 22 based on the operating state AS22 input from the X-ray detector 22, to control, for example, the X-ray detection conditions of the X-ray detector 22.

The rotation device control unit 42 includes, for example, a rotating support base control unit 421, a first robot control unit 422A, and a second robot control unit 422B. The rotating support base control unit 421 outputs a control signal CS31 to the rotation drive unit 312 based on the rotation angle θ31 of the support base 311 input from the rotating support base 31, thereby controlling the rotation of the support base 311. The first and second robot control units 422A and 422B output control signals CS32A and CS32B to the first and second industrial robots 32A and 32B, respectively, based on information such as the angles θ32A and θ32B of each joint input from these robots, thereby controlling the operation of these robots.

The image processing unit 43, for example, receives an X-ray image RI output from the X-ray detector 22 as input and acquires a corrected image CRI by correcting the X-ray image RI. The image processing unit 43 also constructs a three-dimensional CT image 3DRI based on the acquired corrected image CRI, and outputs it to the display device 5. The image processing unit 43 includes, for example, an X-ray image acquisition unit 431, an X-ray image processing unit 432, a correction amount calculation unit 433, a correction amount storage unit 434, an X-ray image correction unit 435, and a three-dimensional image construction unit 436. The operation of each unit of the image processing unit 43 will be described later.

Next, an X-ray image acquisition method P of this embodiment using the aforementioned X-ray image acquisition device 1 will be described. As shown in FIG. 3, when the X-ray image acquisition method P of this embodiment is started, step P1 of capturing a calibration image is performed. In this step P1, for example, the X-ray imaging device 2 and a calibration subject CO (see FIG. 4A) are positioned opposite each other, and an X-ray image of the calibration subject CO is captured by the X-ray imaging device 2 to obtain a calibration image CI.

Figure 4A is a perspective view showing the reference state of the X-ray imaging device 2 and calibration subject CO of Figure 1. Figure 4B is an image diagram showing an example of a reference image SI captured by the X-ray imaging device 2 of Figure 4A. In step P1, first, the X-ray imaging device 2 and the calibration subject CO are positioned facing each other. More specifically, for example, the calibration subject CO is placed and fixed on the support base 311 of the rotating support base 31 of the X-ray image acquisition device 1.

The calibration subject CO is formed from a material such as a metal with a predetermined X-ray transmittance or X-ray absorption coefficient that allows X-ray images to be acquired, and has a rotationally symmetric three-dimensional shape. The calibration subject CO also has multiple portions with different radial dimensions perpendicular to the axis of symmetry. In the example shown in Figures 4A and 4B, the calibration subject CO has a cylindrical shape with different diameters at one end and a radial step in the center along the axis of symmetry. Information such as the three-dimensional shape and dimensions of the calibration subject CO is stored in advance in, for example, a memory or storage device that constitutes the image processing unit 43.

The shape of the calibration subject CO is not particularly limited, as long as it has a rotationally symmetric three-dimensional shape and multiple sections with different radial dimensions perpendicular to the axis of symmetry. The shape of the calibration subject CO can be, in addition to a cylinder with multiple sections with different diameters, a cylindrical shape, a polygonal columnar or tubular shape, one or more solid or hollow spheres, or a shape with multiple concave and convex portions.

The calibration subject CO is supported and fixed to the support base 311 of the rotating support base 31 so that the axis of symmetry of its rotationally symmetric three-dimensional shape coincides with the central axis of rotation A of the support base 311 of the rotating support base 31. Note that if the rotating support base 31 is not rotated when the calibration image CI is captured by the X-ray imaging device 2, or if a non-rotating support base is used, the axis of symmetry of the calibration subject CO coincides with the central axis of rotation A of the X-ray imaging device 2 that rotates around the calibration subject CO.

Next, as shown in FIG. 4A, the X-ray generator 21 and X-ray detector 22 of the X-ray imaging device 2 are brought to face the calibration subject CO. More specifically, the first robot control unit 422A of the control device 4 controls the operation of the first industrial robot 32A, moving the X-ray generator 21 to face the calibration subject CO. The second robot control unit 422B of the control device 4 controls the operation of the second industrial robot 32B, moving the X-ray generator 21 to face the X-ray generator 21 with the calibration subject CO in between.

Here, Figure 4A shows a reference state in which the three-dimensional Cartesian coordinate system of the X-ray imaging device 2 and the three-dimensional Cartesian coordinate system of the calibration subject CO are aligned. Furthermore, Figure 4B shows a reference image SI, which is an X-ray image of the calibration subject CO captured by the X-ray imaging device 2 in the reference state shown in Figure 4A. In other words, the reference state is a state in which the width direction (X-axis direction), depth direction (Y-axis direction), and height direction (Z-axis direction) of the X-ray imaging device 2 are parallel to the width direction (X-axis direction), depth direction (Y-axis direction), and height direction (Z-axis direction) of the calibration subject CO, and the origins of each coordinate system are aligned.

In this reference state, the X-ray generator control unit 411 and X-ray detector control unit 412 of the control device 4 control the operation of the X-ray generator 21 and X-ray detector 22 of the X-ray imaging device 2 to capture a reference image SI, which is an X-ray image of the calibration subject CO. The reference image SI of the calibration subject CO can also be obtained by calculation based on three-dimensional shape information of the calibration subject CO and the positional relationship between the X-ray imaging device 2 and the calibration subject CO in the reference state. The reference image SI of the calibration subject CO is, for example, input to the X-ray image acquisition unit 431 of the control device 4 and stored in the memory or storage device that constitutes the image processing unit 43.

Next, the rotation device 3 including the motor M rotates the calibration subject CO and the X-ray imaging device 2 relatively around the rotation center axis A. More specifically, the rotation support base control unit 421 of the control device 4 rotates the support base 311 of the rotation support base 31, causing the calibration subject CO to rotate around the rotation center axis A of the rotation support base 31, which coincides with the axis of symmetry of the calibration subject CO. Alternatively, without rotating the support base 311 of the rotation support base 31, the first robot control unit 422A and second robot control unit 422B of the control device 4 control the operation of the first and second industrial robots 32A, 32B to rotate the X-ray imaging device 2 around the rotation center axis A around the calibration subject CO.

Then, the X-ray imaging device 2 captures multiple calibration images CI of the calibration subject CO from multiple imaging positions where the two-dimensional shape of the calibration subject CO is the same. The X-ray detector 22 of the X-ray imaging device 2 outputs the captured calibration images CI to the image processing unit 43 of the control device 4. The image processing unit 43 stores the calibration images CI input from the X-ray detector 22 to the X-ray image collection unit 431 in the memory or storage device that constitutes the image processing unit 43. This completes step P1 shown in Figure 3.

Then, as shown in FIG. 3, step P2 is performed to calculate and record image correction amounts. In step P2, the feature amounts of the aforementioned reference image SI are compared with the feature amounts of multiple calibration images CI, and image correction amounts for matching each calibration image CI to the reference image SI are calculated and recorded. More specifically, the image processing unit 43, for example, calculates the feature amounts of the reference image SI and the feature amounts of each calibration image CI using the X-ray image collection unit 431.

Here, the reference image SI is an X-ray image of the calibration subject CO, as shown in FIG. 4B, captured by the X-ray imaging device 2 in the reference state, as shown in FIG. 4A, in which the three-dimensional Cartesian coordinate systems of the X-ray imaging device 2 and the calibration subject CO are aligned, as described above. The X-ray image acquisition unit 431 calculates the feature quantities of the reference image SI and each calibration image CI, such as the outline of the outer shape of the image of the calibration subject CO, the outline of the inner wall of the hollow calibration subject CO, or the shape, dimensions, and position of irregularities and steps.

Figures 5A and 5B, and Figures 6A and 6B respectively show a perspective view and a calibration image CI when the positional relationship between the X-ray imaging device 2 and the calibration subject CO deviates from the reference state.

As shown in Figure 5A, suppose that the X-ray imaging device 2 and the calibration subject CO are rotated relatively around the central axis of rotation A by a rotation device 3 including a motor M, resulting in an angular deviation in the rotation of the calibration subject CO around the Y axis. In this case, as shown in Figure 5B, the image of the calibration subject CO in the calibration image CI is shifted by a predetermined angle around the Y axis perpendicular to the image plane from the image of the calibration subject CO in the reference image SI.

As shown in Figure 6A, suppose that the X-ray imaging device 2 and the calibration subject CO are rotated relatively around the central axis of rotation A by a rotation device 3 including a motor M, resulting in an angular deviation in the rotation of the calibration subject CO around the X-axis. In this case, as shown in Figure 5B, in the calibration image CI, the image of the calibration subject CO is reduced in size in the left-right direction parallel to the X-axis as it approaches the top of the image, in the up-down direction parallel to the Z-axis.

The X-ray image processing unit 432 calculates, for example, feature amounts of the calibration subject CO in a reference image SI such as that shown in FIG. 4B, and feature amounts of each of multiple calibration images CI such as those shown in FIGS. 5B and 6B, which are captured at multiple capturing positions on a circular orbit centered on the rotation center axis A. The correction amount calculation unit 433 then compares, for example, the feature amounts of the reference image SI calculated by the X-ray image processing unit 432 with the feature amounts of each calibration image CI, and calculates an image correction amount for matching each calibration image CI to the reference image SI.

The X-ray image processing unit 432 and correction amount calculation unit 433 can also calculate feature amounts and calculate image correction amounts for the deviation of the calibration subject CO in each axis direction of the three-dimensional Cartesian coordinate system in the calibration image CI. Furthermore, the correction amount storage unit 434 stores the image correction amounts for each calibration image CI calculated by the correction amount calculation unit 433 in the memory or storage device that constitutes the image processing unit 43. This completes step P2 shown in Figure 3. Thereafter, step P3 is performed to capture an X-ray image RI of the subject O, as shown in Figures 1 and 3.

In this step P3, first, object O, such as an automobile part, is positioned opposite the X-ray imaging device 2, similar to the calibration object CO. More specifically, instead of the calibration object CO, object O is placed on the support base 311 of the rotating support base 31. Then, the rotation device control unit 42 of the control device 4 controls the operation of the first and second industrial robots 32A, 32B to position object O opposite the X-ray imaging device 2, similar to the calibration object CO shown in FIG. 4A.

Then, the rotation device 3 rotates the X-ray imaging device 2 and the subject O relatively around the rotation center axis A, and the X-ray imaging device 2 captures multiple X-ray images RI of the subject O. More specifically, for example, the rotation device control unit 42 of the control device 4 controls the rotation of the rotation drive unit 312 of the rotation support base 31 or the rotation operation of the first and second industrial robots 32A, 32B to rotate the X-ray imaging device 2 and the subject O relatively around the rotation center axis A.

Furthermore, the X-ray imaging device control unit 41 of the control device 4 controls the X-ray imaging device 2 to capture X-ray images RI of the subject O from each imaging position where each calibration image CI was acquired. The X-ray detector 22 outputs the captured X-ray images RI to the X-ray image collection unit 431 of the image processing unit 43. This completes step P3 shown in Figure 3. Then, step P4, shown in Figure 3, is carried out to acquire the correction image.

In this step P4, for example, the X-ray image correction unit 435 of the image processing unit 43 acquires multiple corrected images CRI by correcting each of the multiple X-ray images RI of the subject O based on the image correction amount recorded in the correction amount memory unit 434 in the above-mentioned step P2. More specifically, for example, at the imaging position where the calibration image CI shown in FIG. 5B was captured, the X-ray image correction unit 435 corrects the X-ray image RI of the subject O to acquire the corrected image CRI using an image correction amount that rotates the calibration image CI of the calibration subject CO to match it with the reference image SI.

Furthermore, for example, at the imaging position where the calibration image CI shown in FIG. 6B was captured, the X-ray image correction unit 435 corrects the X-ray image RI of the subject O using an image correction amount that enlarges the reduced portion of the calibration image CI of the calibration subject CO to match it with the reference image SI, thereby obtaining a corrected image CRI. The X-ray image correction unit 435 outputs multiple corrected images CRI obtained by correcting each X-ray image RI using the image correction amount corresponding to each imaging position of the subject O to, for example, the three-dimensional image construction unit 436.

This completes step P4 shown in Figure 3. Thereafter, step P5 is carried out, for example, to construct a three-dimensional computed tomography (CT) image. In this step P5, for example, the three-dimensional image construction unit 436 of the image processing unit 43 constructs a three-dimensional CT image 3DRI of the subject O using multiple corrected images CRI. The three-dimensional image construction unit 436 outputs the constructed three-dimensional CT image 3DRI to the display device 5, for example.

The display device 5 is configured, for example, as a liquid crystal display device or an organic EL display device, and displays the 3D CT image 3DRI of the subject O input from the 3D image construction unit 436. This completes step P5 shown in Figure 3, and all steps of the X-ray image acquisition method P of this embodiment.

As described above, the X-ray image acquisition method P of this embodiment includes process P1 of capturing multiple calibration images CI, process P2 of calculating and recording image correction amounts, process P3 of capturing multiple X-ray images RI of the object O, and process P4 of acquiring multiple correction images CRI. In process P1, the X-ray imaging device 2 and the calibration object CO, which has a rotationally symmetric three-dimensional shape and multiple portions with different radial dimensions perpendicular to the axis of symmetry, are arranged facing each other. Then, the calibration object CO and the X-ray imaging device 2 are rotated relatively around a rotation center axis A, which coincides with the axis of symmetry of the calibration object CO, by a rotation device 3 including a motor M. Then, multiple calibration images CI of the calibration object CO are captured by the X-ray imaging device 2 from multiple imaging positions where the two-dimensional shape of the calibration object CO is the same. In process P2, the feature amounts of a reference image SI of the calibration subject CO, captured by the X-ray imaging device 2 under a reference state in which the three-dimensional Cartesian coordinate systems of the X-ray imaging device 2 and the calibration subject CO are aligned, are compared with the feature amounts of each calibration image CI. Then, an image correction amount for aligning each calibration image CI with the reference image SI is calculated and recorded. In process P3, the subject O and the X-ray imaging device 2 are positioned opposite each other, similar to the calibration subject CO. Then, the rotation device 3 rotates the X-ray imaging device 2 and the subject O relatively around the rotation center axis A, and the X-ray imaging device 2 captures multiple X-ray images RI of the subject O from the multiple imaging positions. In process P4, multiple corrected images CRI are obtained by correcting each of the multiple X-ray images RI of the subject O based on the image correction amount.

In the X-ray image acquisition method P of this embodiment, a general motor M, such as that used in the rotary support base 31 of the X-ray imaging device 2 or in an industrial robot 32, is used to rotate the X-ray imaging device 2 and the subject O relatively around the central axis of rotation A to capture a two-dimensional X-ray image. Therefore, unlike the high-precision scanning drive devices used in medical CT devices, the relative position and orientation between the X-ray imaging device 2 and the subject O may deviate from the reference state. Even in such cases, the X-ray image acquisition method P of this embodiment can determine and record the amount of image correction for each imaging position in advance using a calibration subject CO.

Accordingly, according to the X-ray image acquisition method P of this embodiment, X-ray images RI of the subject O, which are captured at each imaging position and contain misalignment due to the motor M, can be corrected into misaligned corrected images CRI using the image correction amount. This allows the cost of the X-ray image acquisition device 1 to be reduced by using a general industrial motor M, and makes it possible to acquire corrected images CRI in which the X-ray image RI has been corrected, even if misalignment occurs between the X-ray imaging device 2 and the subject O in a direction parallel to the rotation center axis A.

The X-ray image acquisition method P of this embodiment also includes a step P5 of constructing a three-dimensional CT image 3DRI of the subject O using multiple corrected images CRI. As a result, even if a general motor M is used and the relative position and orientation between the X-ray imaging device 2 and the subject O deviates from the reference state, it is possible to construct a three-dimensional CT image 3DRI using corrected images CRI in which the effects of this deviation have been corrected.

In the X-ray image acquisition method P of this embodiment, the rotation device 3 includes a rotation support table 31 and an industrial robot 32. The rotation support table 31 rotates around a central axis of rotation A while supporting a calibration subject CO or subject O. The industrial robot 32 positions the X-ray imaging device 2 facing the calibration subject CO or subject O. This dramatically improves the degree of freedom in the position where the X-ray imaging device 2 is installed compared to when a high-precision scanning drive device used in a medical CT device is used, and greatly relaxes the restrictions on the size and shape of the subject O for which an X-ray image RI can be captured.

Furthermore, as described above, the X-ray image acquisition method P of this embodiment does not necessarily require the calibration subject CO or subject O to be rotated relative to the X-ray imaging device 2 using the rotating support table 31. That is, the rotation device 3 can include a mounting table for placing the calibration subject CO or subject O on the rotation center axis A, and an industrial robot 32 that faces the X-ray imaging device 2 toward the calibration subject CO or subject O placed on the mounting table. In this case, the industrial robot 32 rotates the X-ray imaging device 2 around the rotation center axis A around the calibration subject CO or subject O. This makes it possible to capture X-ray images RI of large subjects O that are difficult to rotate using the rotating support table 31.

Figure 7 is a schematic diagram showing a modified example of the X-ray image acquisition device 1 of Figure 1. In the X-ray image acquisition device 1 shown in Figure 1, an example has been described in which the rotation device 3 is composed of one rotation support table 31 and two industrial robots 32, but the rotation device 3 can also be composed of, for example, one rotation support table 31 and one industrial robot 32. In this case, the rotation device 3 can be equipped with a bracket 33 that supports the X-ray generator 21 and X-ray detector 22 of the X-ray imaging device 2 in an opposing position.

The bracket 33 is attached, for example, to an attachment at the tip of the industrial robot 32 and is supported above the calibration subject CO or subject O. In this state, the control device 4 rotates the rotary support base 31, or the control device 4 rotates the attachment at the tip of the industrial robot 32, causing the calibration subject CO or subject O and the industrial robot 32 to rotate relatively around the central rotation axis A.

By using the X-ray image acquisition device 1 according to the modified example of Figure 7, it is easier to adjust the relative positions of the calibration subject CO and subject O and the X-ray imaging device 2 compared to the X-ray image acquisition method P according to the previously described embodiment, which uses the X-ray image acquisition device 1 shown in Figure 1. This reduces the burden of adjusting the imaging system when capturing an X-ray image RI of a portion or multiple locations of the subject O. In addition, it is possible to replace the rotating support base 31 with a non-rotating mounting base and configure the rotation device 3 using only the industrial robot 32 and bracket 33.

Figure 8 is a schematic diagram showing another modified example of the X-ray image acquisition device 1 of Figure 1. In this modified example of the X-ray image acquisition device 1, the rotation device 3 includes a first industrial robot 32A and a second industrial robot 32B, and does not have a rotation support base 31. The first industrial robot 32A holds a calibration subject CO or subject O and places it on the rotation axis A. The second industrial robot 32B, similar to the modified example shown in Figure 7, holds the X-ray imaging device 2 via a bracket 33 and faces the calibration subject CO or subject O. The rotation device 3 rotates the X-ray imaging device 2 and the calibration subject CO or subject O relatively around the rotation axis A using at least one of the first industrial robot 32A and the second industrial robot 32B.

The X-ray image acquisition method P of this embodiment uses the X-ray image acquisition device 1 according to the modified example shown in FIG. 8, and the control device 4 controls the first industrial robot 32A to automate the picking of the subject O, the capture of the X-ray image RI, and the transportation of the subject O after capture. This makes it possible to improve the efficiency of acquiring the X-ray image RI and corrected image CRI of the subject O.

As described above, this embodiment and its modified examples provide an X-ray image acquisition method P that can acquire a corrected image CRI in which deviations in the relative position and orientation between the X-ray imaging device 2 and the subject O, including deviations in the direction parallel to the rotation center axis A, are corrected when a two-dimensional X-ray image RI is acquired by moving the X-ray imaging device 2 and the subject O relative to each other using a general motor M. Therefore, it is possible to acquire a corrected image CRI in which deviations in the X-ray image RI of the subject O caused by the motor M, including deviations in the direction parallel to the rotation center axis A, are corrected, while reducing the cost of the X-ray image acquisition device 1.

The above has described in detail an embodiment of the X-ray image acquisition method and its variations according to the present disclosure using the drawings, but the specific configuration is not limited to this embodiment and variations, and any design changes that do not deviate from the gist of this disclosure are also included in this disclosure.

2 X-ray imaging device 3 Rotation device 31 Rotation support table (mounting table)
32 Industrial robot 32A First industrial robot 32B Second industrial robot 3DRI 3D CT image A Rotation center axis CI Calibration image CO Calibration object CRI Corrected image M Motor O Object P X-ray image acquisition method P1 Process of taking a calibration image P2 Process of calculating and recording image correction amount P3 Process of taking an X-ray image of the object P4 Process of acquiring a corrected image P5 Process of constructing a 3D CT image RI X-ray image SI Reference image

Claims (5)

a step of disposing an X-ray imaging device and a calibration object having a rotationally symmetric three-dimensional shape and a plurality of portions with different radial dimensions perpendicular to an axis of symmetry, and rotating the calibration object and the X-ray imaging device relatively around a rotation center axis that coincides with the axis of symmetry of the calibration object by a rotation device including a motor, and capturing a plurality of calibration images of the calibration object by the X-ray imaging device from a plurality of capturing positions where the two-dimensional shape of the calibration object will be the same if no angular deviation occurs;
a step of comparing feature amounts of a reference image of the calibration subject, which is captured by the X-ray imaging device in a reference state in which the three-dimensional orthogonal coordinate systems of the X-ray imaging device and the calibration subject are aligned, with feature amounts of each of the calibration images, and calculating and recording image correction amounts for matching each of the calibration images with the reference image;
a step of disposing an object and the X-ray imaging device opposite each other in the same manner as the calibration object, rotating the X-ray imaging device and the object relatively around the rotation center axis by the rotation device, and capturing a plurality of X-ray images of the object from the plurality of imaging positions by the X-ray imaging device;
acquiring a plurality of corrected images obtained by correcting each of the plurality of X-ray images of the subject based on the image correction amount;
An X-ray image acquisition method comprising: The X-ray image acquisition method described in claim 1, further comprising a step of constructing a 3D CT image of the subject using the plurality of corrected images. The X-ray image acquisition method of claim 1, characterized in that the rotation device includes a rotation support table that rotates around the central axis of rotation while supporting the calibration subject or the subject, and an industrial robot that positions the X-ray imaging device facing the calibration subject or the subject. The X-ray image acquisition method of claim 1, characterized in that the rotation device includes a mounting table for placing the calibration subject or the subject on the rotation axis, and an industrial robot that faces the calibration subject or the subject placed on the mounting table and rotates the X-ray imaging device around the rotation axis around the calibration subject or the subject. the rotation device includes a first industrial robot that holds the calibration subject or the subject and places it on the rotation center axis, and a second industrial robot that holds the X-ray imaging device and faces the calibration subject or the subject,
2. The X-ray image acquisition method according to claim 1, wherein the X-ray imaging device and the calibration subject or the subject are rotated relatively around the central axis of rotation by at least one of the first industrial robot and the second industrial robot.